Control system



Feb. 26, 1952 E. J. PolTRAs ET AL CONTROL SYSTEM 7 Sheets-Sheet l Filed April ll, 1935 Feb. 26, 1952 E. J. PITRAs ET- AL CONTROL SYSTEM 7 Sheets-Sheet 2 Filed April 1l, 1955 Feb. 26, 1952 E. J. Pon-RAS ET AL CONTROL SYSTEM 7 Sheets-Sheet 5 Filed April ll, 1935 Feb. 26, 1952 E. 1. POITRAS ET AL CONTROL SYSTEM 7 Sheets-Sheet 4 Filed. April ll, 1935 INVENTORS Edward J. Poi/bras 1).Tea/r THEIR AT-oRNEY Feb- 26, 1952 E. J. POITRAS E11 AL 2,586,990

CONTROL SYSTEM Filed April 1l, 1955A 7 Sheets-Sheet 5 f un THEIR ATTORNEY Feb- 26, 1952 E. J. PoxTRAs ET AL' 2,586,990

CONTROL SYSTEM Filed April 1l, 1935 I Y 7 Sheets-Sheet 6 THEIR ATTORNEY lNvENTo s Edwwrd Pai/as Feb. 26, 1952 E, J PQITRAS ET AL 2,586,990 l CONTROL SYSTEM Filed April 11, 19:55 .7 sheets-sheet 7- INVENTORS Edward J Polli/ras Ja//res D. Team msm ATTRNEY atented eb. 26, l95

UNITED STATES PATENT OFFICE CONTROL SYSTEM Edward J. Poitras, Jackson Heights, and James D. Tear, Great Neck, N. Y., assignors to The Sperry Corporation, a corporation of Delaware Application April 11, 1935, Serial No. 15,758

7 Claims.

The invention herein disclosed relates to automatic follow-up mechanisms for controlling the velocity and movement of a driven object in accordance with the movement of a primary movable object, and a mechanism embodying the invention constitutes an improvement on the systern and mechanism illustrated and described in our copending application Serial No. 1,290, iiled January ll, 1935.

In our aforementioned application, there is illustrated and described a mechanism for driving an object in accordance with the movement of another object and the system is specifically applied for movement of a gun mount, the system illustrated being such that a large ordnance piece is moved in exact accordance with a signal without the intervention of a human agency. The system includes a variable velocity driving mechanism which has a control element and is used for moving the driven object. The velocity of the driving mechanism may either be varied manually by direct application to the control element of the physical force of an operator, which mode of operation is known as hand control; or the velocity may be varied automatically through a power-operated actuating mechanism which is controlled in accordance with the difference in movement between the driven object and a movable object the movements of which are to be reproduced Iby the driven object, which mode of operation is known as automatic control. In such systems it has been found to be desirable to provide, in addition to the direct manual or hand control and the automatic control acting in accordance with the diierence between the movements of the movable and driven objects, a control mechanism operating automatically through the power-operated actuating mechanism to effect movement of the driven object to a fixed, predetermined position, for example, to bring a gun to the loading position after it has been iired. It has also been found desirable under certain conditions to effect movement of the gun in response to manual operation of the power-controlled actuating mechanism in order that the driven object may be controlled manually with slight physical exertion on the part of the operator. This invention has for one of its objects the introduction of such controls into this mechanism, and for another object the refinement and simplification of such systems.

These and other objects are realized in accordance with this invention by providing operating mechanism, known as Load Control, for the control of the power-operated actuating mechanism for the control element of the. variable velocity driving mechanism that effects the operation of the actuating mechanism to cause the driving mechanism to move the driven object t a liked, predetermined position; and by providing other operating mechanism, known as Local Control, for the control of the said power-operated actuating mechanism which operating mechanism is manually operative. These operating mechanisms and the automatic control may be selectively rendered eiective for operating the power-operated actuating mechanism, and the power-operated actuating mechanism and hand control may be selectively rendered effective for actuating the control element of the variable velocity driving mechanism.

These improvements are incorporated in a mechanism illustrated in the accompanying drawings which mechanism is particularly suitable for moving large ordnance pieces.

In the drawings:

Fig. 1 is a plan of a complete apparatus embodying the invention;

Fig. 2 is a side elevation of the same modified to show schematically the movable object and its connection to the receivers of the self-synchronous electrical transmission system;

Fig. 3 is a side elevation, partly in section, of the variable velocity hydraulic gear or driving mechanism portion of the apparatus;

Fig. 4 is a diagrammatic illustration of the amplifier and diierential for the hydraulic gear or driving mechanism;

Fig. 5 is a longitudinal section of the mechanism for actuating an element of the control for the hydraulic gear or driving mechanism;

Fig. 6 is an end view of a cam;

Fig. 7 is a longitudinal elevation of the same;

Fig. 8 is an end view of another cam;

Fig. 9 is a longitudinal elevation of the same;

Fig. 10 is a longitudinal section of mechanism for actuating another element of the control for the hydraulic gear or driving mechanism;

Fig. 11 is an end elevation of the same and shows a 4part of the control for the hydraulic gear or driving mechanism;

Fig. 12 is a fragmentary elevation of a receiver and the local and loading control mechanism;

Fig. 12a is a sectional view oi a block shown in Fig. 12;

Fig. 13 is a sectional plan of the same taken on the line I 3-l 3 of Fig. 12';

Fig. 14 is a fragmentary elevation, party in section, of the same at ninety degrees with respect to the elevation illustrated in Fig. 12;

Fig. l5 is a sectional elevation of the hand control mechanism taken along the line I 5,-!5 of Fig. 1; and

Fig. 16 is a transverse section of the same taken along the line IS-IG of Fig. 15.

GENERAL DESCRIPTION The movable and driven objects may take many forms, for example if the system be used for driving the rudder of a vessel, the movable object will be the control levers and the driven object the rudder, and if the system be used in ordnance for which the mechanism illustrated is particularly suitable, the mechanical element of the gun fire control mechanism lthe movement of which is to be followed will constitute the movable object and the gun the driven object. In any event, the movable object is mechanically connected to two generators of a selfsynchronous electrical system, yone of which opf erates in a one to one ratio with the movable object and the other of which operates at some higher ratio with respect to the movable object such, for example, as thirty-six to one. These generators are electrically connected to receivers I and 2 respectively which constitute a factor in controlling a variable Avelocity driving mechanism shown as a hydraulic gear 3 through which a shaft II, connected to the output end of the hydraulic gear and the driven object, is driven. The input end of the hydraulic gear is connected to a constant speed electric motor 5.

The hydraulic gear 3 is of -a well known type such as that disclosed in United States Letters Patent No. 925,148 granted June 15, 1909, to H. D. Williams for Variable Speed Gear, with certain modications which will appear in the detailed description of the several Vparts of the system. Essentially, the hydraulic gear includes a hydraulic pump known 'as the A`end and driven by the electric motor 5, and a hydraulic motor known as the B end and connected to the shaft 4. The A and B ends are identical in construction with one exception. Each consists of a series of cylinders about and parallel to the longitudinal or shaft axis of the gear. The cylinders of the pump and the motor extend in opposite directions and are separated -by a stationary valve plate through which they communicate. The forces acting upon reciprocating pistons in the cylinders are resolved into component forces which are so utilized that in the pump rotary movement of the pistons is converted into vreciprocating movement, and in the motor reciprocating movement of the pistons is converted into rotary movement. This conversion is effected by plates or boxes inclined to the axis of the gear shaft. The inclination of the motor plate is xed but the plate 6 (Fig. 3) or tilting box, as it is commonly called, of the pump is mounted so that its angle of inclination with respect lto the axis of the shaft may be varied to vary the length of the stroke of the pistons or to change their Vphase relation. It is by varying the inclination of this tilting box that the velocity, both speed and direction of the motor may be varied.

Movement of the driven object is controlled by moving the tilting box of the hydraulic gear, the direction of movement of the driven object being dependent upon the direction in which the tilting box is moved from its neutral position, i. e. perpendicular to the axis of the shaft, and the speed of the movement of the driven object being dependent upon the extent the tilting box is moved from Yits neutral position. 'Ihe tilting box therefore may be called a control member. When the system is in operation, the'tilting `box is moved from its neutral position in accordance with the diierence in movement between the movable object, represented by the receiver motors I and 2, and the driven object, represented by the shaft 4. In actual operation the receiver motor 2 acts as a Vernier and normally assumes the control of the movement of `the'tilting box.

4 The receiver motor I takes over control whenever the movable and driven Objects are out of phase more than a few degrees, as, for example, when synchronizing or during conditions of rapid acceleration and deceleration, and at all times acts to maintain the synchronous relation of `the movable and driven objects.

The receiver motor I and its associated control mechanism is connected at a low ratio, for example, one to one, to both the movable object and the driven object, while the receiver motor 2 and its associated control mechanism is connected at a higher ratio, for example, thirty-six to one, to both the movable object and the driven object. The connections from the receiver motors to the movable object are electrical and the connections to the driven object or shaft 4 are mechanical in the embodiment shown. These connections and their operation to effect movement of pilot valves in accordance with the difference in movement between the movable and the driven objects Vare hereinafter described.' These pilot valves control a hydraulic amplier and differential (Figs. 2

and 4) which eiects the operation of a hydraulically operated piston connected to the tilting box of the hydraulic gear.

A yieldable connection designated generally by the reference character 8 in Figure 2, between the differential through which the receiver 2 acts and the pilot valve operated by the output of the differential, permits the operation of the tilting box through the hydraulic amplifier for both load control and local control, a manually operable shaft as later described enables the operator to manipulate the hydraulic amplier manually for local control with slight physical effort. The several controls are individually rendered effective by the manual operation of a lever I0 (Figs. 1 and 4) which actuates a selector valve in the hydraulic amplifier 1 to bring one or the other of the controls into operation depending upon the position of the valve. The selector valve also controls a hydraulically operated clutch II through which the tilting box of the hydraulic gear may be operated by the direct application of the physical force of an operator exerted through hand-wheels I2.

AUTOMATIC 'OPERATION Within the hydraulic amplifier designated generally by the numeral 'I and shown diagrammatically in Figure 4, there is a piston I3, reciprocally mounted in a cylindrical compartment I4. The piston I3 is Yconnected to the tilting box of the hydraulic gear by a piston rod I5 which extends into the hydraulic gear and is enlarged at I5a at which point it is provided with an opening to receive a stud I6 extending from the tilting box, the connection being as shown in the nature of a universal joint. The piston is thus directly connected to the tilting box and the tilting box is moved from its neutral position, perpendicular to the axis of the hydraulic gear, in accordance with the movements of the piston. Fluid under pressure is admitted to and exhausted from the cylindrical compartment I4 containing the piston to control movement of the piston by a piston valve I1. This valve is in turn actuated in accordance with the difference in the movements of a yplunger I8, the action of which is controlled by a pilot valve I9, and of the piston I3. The operation is accomplished by the interv connection of the several parts as illustrated diwhich oneface a, that having the piston rod connected thereto, the upper face as seen in Figure 4, is one-half of the area of the opposite or lower face b. With this arrangement, the same pressure acting upon the face b creates a force twice as great as the force created by the same pressure acting upon the face a of the piston I3. The chamber i 4a of which the face a of the piston I3 forms an end wall is directly connected through a passage and a pipe 2I to a pump 22. The pump is of the rotary type capable of furnishing a uid under a pressure of 600 or more pounds per square inch, and it is directly connected to the shaft of the motor 5 through gears 22 and 22" (see Fig. 2). The pressure delivered by the pump to the passage 29 is maintained at a constant pressure, preferably 600 pounds per square inch, -by a constant pressure valve 23 which is connected to the high pressure pipe 2| and a pipe 2 4 connected to the intake side of the pump. Fluid under a constant pressure of 600 pounds per square inch is. therefore, maintained in the chamber Illa of the cylinder I4. A branch passage 25 connects the high pressure passage 20 to a port in which the valve I1 is mounted. Another port communicating with the valve compartment 25 is connected by a pass-age 21 and a pipe 28 to the intake side of the pump, the passage 21 constituting an exhaust passage. The chamber Mb formed in the cylindrical compartment I4 and having the piston face b as one wall thereof is connected by a supply passage 29 to a port communicating with the valve chamber 26 and midway between the pressure and exhaust ports. The piston valve I1 is of the usual type having a reduced section at its axial center and when in the oif position, it laps the pressure and exhaust ports. If, however, the valve is moved upwardly from the position shown in Figure 4, the pressure port is con- .i

nected to the passage 29 and uid at a pressure of 600 pounds per square inch is admitted to the chamber I4b. Since this creates a force on the surface b of the piston twice as great as the force acting on the surface a of the piston, the piston will be moved upwardly from "the position shown in Figure 4. Likewise, when the valve is moved downwardly from the position shown, the exhaust passage 21 is connected to the passage 29 and the pressure in the chamber I4b is reduced so that :t

the force acting upon the face a 4of the piston causes the piston to move in the opposite direction. With this arrangement movement of the piston is controlled by the single piston valve I1.

The piston valve I1 is hydraulically operated and it is, like the piston I3. of the differential type. The piston valve I1 has a face a of onehalf the area of the face b. The portion 26a of the valve chamber of which the face a of the piston valve I1 forms one wall, is connected by a passage 39 to a reducing valve 3|. The reducing Valve 3| is vin turn connected to the high pressure by a pipe 32 and to the exhaust by a pipe 33. This reducing valve is of the usual type and supplies uid under pressure at approximately 100 pounds per square inch. The opposite end of the valve compartment 26, that is, the section 26h of which the face b of the piston valve forms a wall, is connected by a branch passage 34 to a passage 35. The passage 35 connects a variable volume chamber 36 formed in the piston I3 and the piston rod I5 with the lower end 31o of the plunger compartment 31 in which the plunger I8 is mounted.

The variable volume chamber in the piston I3 chamber 31a.

axially of the piston and piston rod. Into this hole there is inserted a tube 38 which is slidably mounted therein and which forms a snug t with the walls thereof. The tube is connected at one one to the head of the cylindrical chamber I4. As the piston moves, the chamber 38 is enlarged or contracted. This chamber 36, the chamber 262i of the valve chamber 26, and the chamber 31h of the valve compartment 31 contains fluid under a pressure of one-half the pressure in the passage 30, that is, pounds per square inch. The volume formed by this chamber and these com partments constitutes what is termed a reference volume.

The extended section |1c of the piston valve I1 which is provided to form a surface a of one half the area of the surface b extends into a chamber I1d which is connected by a passage 33 to the exhaust passage 21. Thus, when the .pressure in the chamber 26a is 100 pounds per square inch and the pressure in the chamber 25h is 50 pounds per square inch, the piston valve I1 is balanced and there is no movement. The reference volume, that is, the chambers and pascommunicating with the valve compartment 26 .f Sages determining the reference volume constitute a closed system. The balanced condition of the valve may, therefore, be disturbed and the valve actuated by varying the volume of a charnber forming apart of the reference volume. The reference volume may be and is, in the operation of the system, affected by movement of the plunger I8 and the piston I3.

Movement of the plunger I8 is controlled by the pilot valve I9, as heretofore stated. The pilot valve I9 is mounted within the plunger it self in a valve compartment Ia. To one end of this valve there is connected a valve rod 39 which extends through the end of the plunger. The plunger has a longitudinal groove IBb formed in its surface and connected by a passage 4G to the low pressure passage 30. A bore Ic transverse of the plunger connects the groove |81)- with the valve compartment I8a. The valve IS has two reduced sections I9a and I9b. The passage Hic connects with the valve compartment at the reduced portion I9a of the valve I 9, when the valve is in its neutral position or midway between the ends of the valve compartment, which is the position shown. A passage Id through the plunger connects the chamber 31a of the plunger compartment with the valve compartment. The port through which the passage |811 is connected to the valve compartment Ia is spaced from the port through which the passage I8c connects with the valve compartment lila. Another passage I8e connects the valve compartment i3d with a groove I8f in the surface of the plunger which in turn is connected by a passage il to the exhaust passage 21. l

With this arrangement, it will be observed 'that if the Valve I9 is moved downwardly from the position shown in Figure 4, fluid under pressure willvpass through the passage 39, the passage40, groove |817, passage |80, passage iSd to The fluid under pressure in the chamber 31a acting upon the face of the plunger will cause the plunger to move down and com tract the chamber 31h, thus, altering the distribution of the volumetric space of the closed system. This movement Vof the plunger will react upon the face b of the valve I1 and cause the valve to move to a position in which the passage 25 is placed into communication with the passage 29. Oil under high pressure, then enters the chamber and the piston rod I5 is formed by boring a hole 7; |41) randuaots upon the face b of the piston I3 causing the piston to move VupWardly from the position of Figure 4. This movement of the piston moves the tilting box to which it is directly connected. As a consequence -of the movement of the piston, however, the variable volume chamber 36 is enlarged, thus tending to reduce the pressure in the 'closed system. The volume of the chamber 36 will increase 'until the valve I1 under the force of the pressure on the face a, moves back to a .position -in which the high 'pressure and exhaust ports are lapped. If on the other hand, the valve rod 39 is moved upwardly,

the passages I8e and Id will be placed in communication as the reduced section I9b of the valve I9 will bridge these two passages. The plunger chamber 37a will then be placed into communication with the exhaust Ypassage 4I, and the pressure passage I8c 'will be cut off 'from communication with rthe 'passage I'8d. Due to the pressure acting upon the face a ofthe piston valve I'! and the connection of the plunger chamber 31a to the exhaust, the (piston Ivalve will move downwardly and the passage 29 'and the exhaust passage 2l will be bridged by rthe reduced portion of the valve Il and placed into communication. The uid pressure in the chamber I4b will then be reduced and the piston I3 will move downwardly under the force of the fluid acting upon the face a of the piston. This action will cause the chamber 36 to be contracted and will thus increase the pressure in the valve chamber 25h until the valve II cuts off the passages 25 and 2.

It is to be noted that the plunger i8 follows the valve I9; in fact, in actual operation the difference in movement between these elements is imperceptible. The effect, however, is 'that while movement of the valve opens the chamber 37a either to fluid under pressure or to the'exhaust, the plunger follows the valve and the neutral relation of the plunger and valve is restored in the new position of the valve. Movement of the valve to a position from that lshown in the drawings to another position, therefore, causes a delinite movement of the punger I8 and as above explained a definite movement of the plunger causes the piston I3, and consequently the tilting box, te be moved from the neutral position a definite amount proportional to the movement of the plunger I8 and, therefore, of the valve I9'. 4llfhen the valve I9 is moved from the position shown in Figure 4 and held in the new position a period of time, the B end of the hydraulic gear operates at a constant velocity over that period ci" time, the direction of movement being dependentA Advancing valve As heretofore stated, the pilot valve I9 is actuated in accordance with the difference in movement between the movable and driven objects, through means hereinafter specifcallydescribed, and, therefore, the driven object must lag behind the movable object before movement of the valve is eiected. However, when the driven object is in movement, it is desirable to bring it into positional agreement with the movable object or signal and for this purpose there is provided a valve controlled by the plunger I8 for admitting uid to and exhausting it from rthe .reference volume. The valve consists of a cylindrical element -42 secured at one end in the head of the plunger compartment 31 and extending into a. recess |89 in the plunger in which it is slidably mounted. The cylindrical element 42 has the end thereof which is received in the recess in the plunger closed except for a small opening 42a. therethrough, the edges of which form a. valve seat. for a needle valve 43. The needle valve has an enlarged threaded end section 43a which is threaded in an enlarged recess in the open end of the cylinder 42. The needle valve can vthus b'e adjusted with respect to vits seat. Through the side wall of theA cylindrical element 42, there are two openings 42h and 42e spaced from each other longitudinally of the cylinder. The 4inner end of the recess I3g in the plunger is connected rby a. passage I8h to the chamber 3!11. A passage |8111 connects the groove I8b in the surface vof the plunger to the recess Ig at a point adjacent 'and above the opening 42h in the wall of the cylinder 42 as seen in Figure 4, and a passage |87 connects the -recess |89, at a point adjacent and below the opening 42e, to a longitudinal groove I8f .in the surface of the plunger. Thus, as the plunger moves down and increases the pressure of the reference volume, the passage I8i communicates with the opening 42h and the interior 'of the cylinder 42. Fluid under pressure, therefore, flows through the passage 40, groove 18D, passage I8i, cylinder 42, needle valve opening 42a and passage 48h to increase the pressure in chamber 3'l'b and augment the effect of the downward movement of the plunger. If on the other hand the plunger moves upwardly, then the passage I8 is placed in communication with the interior of the cylinder 42 by registering with the opening 42C. The flow of fluid is then reversed; it passes from the chamber 31o through the passage I8h, needle valve opening 42a, opening 42e, passage 18.7', groove I8f and to exhaust passage 4I. Thus, the reference volume is decreased and the effect of the movement of the plunger augmented. The adjustment of the needle valve 43 is empirical and depends upon the conditions of service.

The piston valve I1 contains limiting ports and passages I'Ic and Ilf to relieve the valve in the event of extreme movement. The passage |16, in the event the valve is moved downwardly to an extreme position connects the chamber 2Gb to the pressure passage 30 and thus admits .pressure to the chamber 2Gb to raise the valve. If the valve is moved upwardly t0 an extreme position, the passage I'lf connects the chamber 2Gb` to exhaust passage 2'! and thus relieves the pressure in chamber 25D. These limiting ports and passages thus act as limit stops, and in addition they serve to maintain the proper volume, and `regulate the pressure of the oil in the reference volume.

Synchronous 'valve Due to the high ratio, thirty-six to one, of the mechanism operating the valve I9 With respect to the movable and driven objects, the movable and driven objects might get out of synchronism and in order to maintain the synchronous rela'- tion there is provided a valve 44 which, when'the movable and driven objects are a few degrees out of phase, takes over control of the pilot valve I9, this `being permitted by the flexible connection between the valve rod 39 and the driving mechanism therefor, previously mentioned and hereinafter described in detail. The valve 44 is an ordinary piston valve having a reduced central portion 44a. Through a valve rod 44h, the valveis connected for operation in accordance with the diierence in movement of the movable object,

the valve compartment IBa.

the receiver 2, and the driven object in a one to one ratio. The valve compartment 45 in which the valve is mounted is connected by two passages 46 and 41 spaced longitudinally of the valve to the plunger compartment 31. The passage 46 communicates with a, groove I8lc in the surface of the plunger extending longitudinally of the plunger and communicating with a passage |8Z and through a restricted passage |8m with the passage |80. The passage 41 communicates with a groove |81 in the surface of the plunger extending longitudinally of the plunger and communicating with a passage |80 and through a'restricted passage |810 with the passage |8c. The passage |81 also communicates with the chamber formed between the upper end of the valve I9 and the upper end of the valve compartment |8a. and the passage |80 communicates with the chamber formed between the lower ends of the valve I9 and the valve compartment.

When the valve 44 is in the neutral position as shown in Figure 4, the reduced portion of the valve bridges the passages 46 and 41 and places these passages in communication with an exhaust passage 48 connecting the valve compartment 45 with the exhaust passage 4|. There is, therefore, no elfect upon the valve I9. If, however, the valve 44 is moved so that the passage' 41 is closed, uuid sowing from the passage m` through the restricted passage |817, groove |811.,

and passage I 8o will build up pressure in the lower chamber of the valve compartment I8a. The upper chamber of the valve compartment will be connected to the exhaust through the passages |81, I81c, 46, valve 44 and passage 48. The pressure in the lower chamber will, therefore, move the valve I9 upwardly from the position shown in Figure 4. On the other hand, if the valve 44 is moved so that the passage 46 is closed pressure will be created in the upper chamber of the valve compartment I8a and the lower chamber will continue to be connected to the exhaust. In this way the valve I9 is moved rapidly and fully, speeding up the movement of the driven member.'

Selector valve When the valve I9 is to be operated manually, or operated to bring the driven object to a xed predetermined position, which may be done as hereinafter described, the valve 44 must be rendered inoperative. This is accomplished through a selector valve 49, that is actuated by the lever IU. The valve 49 is slidably mounted in a valve compartment 50. Passages 5I and 52 connect respectively passages 46 and 41 to the valve compartment 50. position shown, the passages 5I and 52 are blocked off by the valve. In any one of the other three possible positions of the valve, however, these passages are connected to the exhaust and, therefore, it is impossible to build up pressure in the passages 46 and 41 or the chambers of Thus, the Valve 44 cannot have any eiect upon the valve I9 when the selector is in any position other than that for automatic operation as illustrated. The selector valve is hollow and the lower end of the valve compartment communicates with the high pressure passage 28, through a passage 53. There is also a transverse passage 49a through the valve at the longitudinal center thereof. On one side of this passage, the upper as seen in Figure 4, the valve is reduced in diameter for a considerable portion of its length, suflicient to bridge three longitudinally spaced passages 54, 55 and 56 which communicate respectively with exhaust When the selector valve is in the passage 48, the hydraulically operated mechanism for bringing into operation the mechanism for moving the driven object into a xed predetermined position, and through the pipe 56a, the mechanism for bringing the manual control of valve I9 into operation. In this reduced area, there is a block 49C which laps the passages 5I and 52 in the automatic position of the valve. Below the passage 49a there is a groove 49d which normally bridges passage`56 and a passage 51 which communicates with the exhaust passage 54.

The selector valve has four possible positions as indicated, called Load, Automatic, Local and Hand. In the automatic position, passages 5|, 52 and a passage 58 communicating with the valve compartment and passage 29 are blocked off. The passage 49a and the longitudinal passage through the valve are also cut off and the passages 54 and 55 are in communication, as are also the passages 56 and 51. In the loading position, `which brings into operation the mechanism for moving the driven object to a fixed predetermined position, the passages 5I and 52 are placed in communication with the exhaust passage 54; the passage 49a, communicating with the high pressure passage 53 through the longitudinal passage through the valve, is placed in communication with the passage 55 which,-

through a pipe 59, supplies oil under pressure to a loading clutch which renders the loading mechanism operative; and the passages 56 and 51 are continued in communication. When the valve is moved to the local position, that is, the position for the hand operation of the valve rod 39, the passage 49a is placed in communication with the passage 56, and the passages 5I, 52 and 55 are in communication with the exhaust passage 54. In the hand position of the valve, in which position, the hydraulicA operation of the tilting box is rendered inoperative and the tilting box may be operated by the direct application of the physical force of an operator to the tilting box, the passage 49a. connects the passages 58 and 51. Thus, the passages 58 and 53 are placed in communication with the exhaust so that the intake and exhaust sides of the pump are directly connected and there is no pressure created. The hydraulic actuating means for the tilting box, therefore, becomes inoperative.

Pilot valve control The synchronous receiver 2 is mounted on a plate 6!) by means of straps 6I and 62. The mechanism which actuates the valve rod 39 is connected to the, shaft of the synchronous receiver 2 through a cylindrical tting 53l (Fig. 5) pressed on to the shaft. the e'nd of the fitting 63 is substantially reduced iny diameter and receives a machine screw 64. Tofthe inner end portion of the fitting 63, there is secured a bracket 65 having a depending arm 66 to which one end of a bifurcated lever 61 is pivotally secured. On the free end of the bifurcated lever 51, there is rotatably mounted a cam follower 88. The bracket 65 is secured on to the tting 63 so that it will rotate therewith. The cam follower 68 cooperates with a cam surface formed on the edge of a cylindrical cam 69. The cam with which the follower 68 cooperates is a constant rise cam, that is, it has a constant rise from a low point to a high point diametrically opposite the low point. As shown in Figures 5 to '7, inclusive, the cam 69 has an intermal flange 69a of considerable width which is The opening through,

rotatably mounted upon the fitting 63 by ball bearings 12 held on the fitting 63 between collars and 1 I. The collar 10 abuts against a circumferential ange 63a formed on. the fitting 63 and the collar 1| is held in place by a washer 13 secured to the end of the fitting 63 by the ma chine screw 64. The cam also has a skirt 69h which extends axially from the flange 69a in a direction opposite to the cam surface. The skirt 69h has a pair of diametrically opposite longitudinal slots 69C. The cam follower 68 is held against the cam surface by a spring 14 which is connected at one end to the lever 61 and at the other end to the ange 53a. This arrangement provides a relief coupling between the receiver and the cam 59. When the reaction on the cam 69 does not exceed a certain definite value, the cam follower will remain at the low point of the cam and the cam will rotate with the cam follower. If, however, the torque exceeds the value for which the cam is designed, the cam follower will rise along the surface of the cam. When the torque lessens, the cam and cam follower will resume their normal relation.

The skirt 69h of the cam 69 is surrounded by a positive cam 15. (See Figures 5, 8 and 9.) The cam 15 is a cylindrical member having diametrically opposite helical grooves or slots 15a of a substantial pitch. This cam is received in a bushing 16 to which it is secured against relative rotational movement. The bushing 16 is journaled in a bearing 13 which is supported by a bracket 19 secured to the plate 60. At one end, the upper end as seen in Figure 5, of the bushing 16 there is secured to the bushing a gear 80.

Within the skirt of the cam 69 and extending transversely thereof through the slots therein and into the cam grooves 15a of the cam 15, there is a pin 8|. To the pin 8| there is pivotally secured one end of a bifurcated link 82 and to the other end of this link the valve rod 39 is secured.

It will be observed that any relative movement between the skirt 60h of the cam cylinder 69 and the cam cylinder 15 will effect a movement of the pin 8| longitudinally of the cams and consequently a movement of the valve rod. In the neutral position or the olf position of the pilot valve I9, the pin 8| extends into the grooves 15a in the cam 15 at the point where these grooves cross each other when projected on to a plane such as illustrated in Figure 9, that is, midway of the grooves. Consequently, relative movement between the cylindrical cam 69 and the cam 15 in one direction will effect longitudinal movement of the valve rod in a particular direction from this neutral position and relative movement of the cams in the opposite direction will effect movement of the valve rod in the other direction.

As previous explained, the cam 69 is normally rotated with the shaft of the receiver 2. The bushing 16 through the gear 80 is rotated in the same direction as the rotation of the cam 69 in accordance with the movements of the driven object. For this purpose, the gear 80 is connected to the shaft of the B end of the hydraulic gear. This connection includes the gear 80, a gear Bla meshing with the gear 80, as shown in Figures l and 2, and mounted on a shaft 82 journaled in bearing brackets 83 secured to the plate 60, a gear 84 mounted on a shaft 85 for rotation therewith and meshing with the gear 8Ia. On the shaft 85, shown in Figure 1, there is mounted a bevel gear 86 which meshes with a bevel/.gear

8-1 secured on the end of afshaft 88 that extends longitudinally of the hydraulic Vgear and is mountedV in bearing brackets 89 and 00 secured to the side ofthe hydraulic gear. On the opposite end of the shaft 88' there is mounted a spur gear 9| which meshes with a gear 02 mounted on the shaft of the B end of the hydraulic gear. The ratio of the gear train just described is such that the gear 80, and consequently the cam ,15, is rotated at a speed of thirty-six revolutions for each revolution of the object driven by the shaft 4. As heretofore stated, the receiver 2 operates in a ratio of thirty-six to one with respect to the signal or movable object. The movement of the valve rod 39, therefore, represents the difference in movement between the movable and driven objects in a ratio of thirty-six to one. v

The' synchronous valve 00 is operated through the receiver I whichV constitutes an electrical dife ferential (see Figures 10 and ll). The stator of the receiver I is rotatably mounted in brackets 93' and 94 secured to the plate 00, `as shown in Figure 2.A On the end of the shaft of the receiver I, there is mounted a constant rise cylin drical cam 95, best shown in Figure 10, the cam surfaceof which is the same as that of the cam 69. Rotatably mounted on the shaft of the receiver there is a bushing 95 to which a bracket arm 91 is secured. To the bracket arm 91 there is pivotally secured one end of a bifurcated lever' S8 and on the free end of the lever there is rod tatably mounted a cam follower 99 which engages the cam surface cf the cam $15. The bracket 91 has an arm 91a extending at right angles thereto. To the arm 01a there is Secured the end of the valve rod 44h. An L-shaped bracket |00 isalso secured to the bushing S0 at a point diametrically opposite to the bracket 91. A spring 0| is connected at one end to the bracket |00 and at the other end to the free end of the lever 98, the spring acting to maintain the cani follower against the surface of the cam 95. The stator of theV receiver i has secured.y thereto a gear |02 (see Figures l and 2) which meshes with a worm |03 mounted upon a shaft |04 jour--A naled in the plate 60 and a bracket |05 secured to the hydraulic amplifier 1. The shaft |04 ex tends through the plate G9 and on the end thereof there is secured a beveled gear I 06 which meshes with a beveled gear |01 secured on the shaft 85, as shown in Figure 1, Since the shaft is, as heretofore stated, driven from the shaft of the B end of' the hydraulic gear, the statorof the receiver I is also driven in accordance with" the shaft of the B end of the hydraulic gar'. The ratio of gearing is such that the stator of the receiver I is rotated at the same speed as the driven object. Since the stator is rotated relatively in a direction opposite to that of the movable object, movement of the shaft of the receiver I represents the difference in movement between the movable and driven obiects in a one to one ratio. The movement of the shaft of the receiver is transmitted through the cam and cam follower 89 to the valve rod 44h, the cam follower and the bracket 91 to which it is' secured being moved in accordance with themovement of the cam within the torque limitations of this relief connection. The arrangement is such that the synchronous valve operates totake the control of the pilot valve away from the receiver 2 through the operation of the receiver" I only when the difference between the movements of the movable and driven objects exceed ay certain predetermined amount.

LOCAL CONTROL As heretofore stated, the valve rod 39 may be actuated manually to effect the operation of the hydraulic gear. This manual operation is effected through a disk |08 secured to the cam 69 and having a beveled edge portion, as shown in Figures 5 and 12. The disk |08 is adapted to be driven by a beveled driving wheel |09 secured on a stub shaft H and adapted to engage with the beveled edge portion of the disk. The stub shaft H0 extends through and is journaled in the web section of a U-shaped bracket III, the arms IIIa and IIIb of which are pivotally mounted upon a shaft H2 as illustrated in Figures 13 and 14. The shaft H2 is journaled in bearing brackets II3 and ||4 secured to the plate 60. On the end of the shaft H0, opposite to that end on which the friction wheel |09 is mounted, there is mounted a bevel gear II5, secured to the shaft for rotation therewith. The bevel gear I|5 meshes with a bevel gear H6 mounted on the shaft H2 for rotation therewith. The U-shaped bracket III is normally maintained in an elevated position, such that the friction wheel |09 does not engage the disk |08, by a spring H1 secured at one end to the web of the U-shaped bracket and at the other end to a stud I I8 secured in the bracket 62, as shown in Figure 14. The shaft H2 may be rotated manually by a crank arm H9 which is secured to the shaft, as revealed in Figure 12. The crank arm H9 may be located at any convenient place.

The friction wheel I 09 is brought into engagement with the disk |08 by shifting the lever I0 to the local control position. As heretofore stated, when the lever I0 is moved to the local control position, the valve 49 is so positioned that the transverse passage 49a therethrough is placed in communication with the passage 56, and it is thus connected to the high pressure passage 53. The passage 56 is connected to a passage |20 in a block |2I (see Fig. 12) secured to the plate 60. Within the block I2I, there is a plunger compartment |22 in which there is mounted a plunger |23 having a reduced central portion |23a. The passage |20 connects with the plunger compartment behind the plunger. When the passage 56 is thus connected with the transverse passage 49a, uid under pressure enters the plunger passage in the block I2| and acts upon the plunger. The plunger is thus forced upwardly from the position shown in Figures 12 and 14 and causes the U-shaped bracket III to move about the shaft H2 as an axis. The action is such that the friction wheel |09 is pressed against the disk |08 so that there is a frictional engagement between the wheel and the disk.

It is to be noted that the passages 5| and 52, as heretofore stated, are connected to the exhaust when the valve 49 is in the local control position so that the valve 44 cannot effect the operation of the valve I9. It will thus be seen thatl the local control, or manulal control through the hydraulic amplifier acts through the cam 69. Rotation of the shaft H2 through the crank arm I I9 eifects rotation of the disk and consequently of the cam 69 to which the disk is secured against relative rotational movement. The driven object will therefore follow acurately the movements of the crank arm H9 since the motion transmitting train between the gear 80 and the B end of the hydraulic gearwill cause the valve rod to be moved in accordance with the difference in movement between the crank arm I9 and the movement of the hydraulic gear or the driven object. When the local control is in operation, the cam follower 68 rides up the cam 69 and the receiver 2 has no effect upon the actuation ofthe valve rod 39.

LOAD CONTROL The mechanism for moving the driven object to a fixed predetermined position also acts through the valve I9. This mechanism includes a positive cam |24 (Figs. 13 and 14) whih consists of a circular disk having a cam groove in one surface thereof. The cam groove consists of two concentric circles I24a and |241) connected by a section |240. The cam is mounted upon a shaft |25 journaled in bearings secured to the plate 60. Also mounted upon the shaft |25 is a beveled gear |26 (see Fig. l.) which meshes with a beveled gear |21 mounted upon the shaft 85. Since the shaft is connected to the B end of the hydraulic gear, the cam |24 will be rotated in accordance with the move-- ments of the hydraulic gear. The ratio of the gear train between the B end of the hydraulic gear and the cam shaft |25 is such that the cam shaft I 25 makes but one revolution on either side of the load position for the entire movement of the driven object. Extending into the groove in the cam |24 there is a cam follower |21a which is secured to and extends laterally from a lever |28 adjacent one end thereof. The lever |28 is pivotally mounted, between its ends. on a pivot |29 and adjacent its opposite end the lever has a second laterally extending pin |30, as shown in Figure 14. Also mounted upon the pivot |29, there are a pair of jaws I3I and |32. These jaws have forked ends through which the valve rod 39 passes and they are normally held separated by a spring |33. On the valve rod 39 there is a ball |34 positioned between the jaws |3| and |32. When the cam follower |21 is in thev section I24c of the cam groove and midway between the outer and inner circles, the lever |28 is substantially perpendicular to the plane of the plate 60 and it is in this position when the driven object, or the gun in the case of ordnance, is in the loading position. When the jaws are closed and engaging the ball A|34 and the lever is in this position, the valve |9 is constrained in its neutral position and the hydraulic gear is at rest; when the jaws are closed in any other position of the cam follower in the cam groove, the valve I9 is displaced from its neutral position and the hydraulic gear is in motion.

The load control mechanism is brought into operation to actuate the valve rod 39 by moving the control lever I0 to the load position. When the valve 49 is moved to the load position the passage 49a is placed into communication with the passage 55 so that uid under pressure is delivered to the passage 55. The passage 55 connects through pipe 59 with a passage |35 (see Fig. 12) in the block |2I. The passage |35 communicates with a passage |36 at its longitudinal center. One end of the passage |36 communicates with a passage |31 which connects the passage |36 to one end of a plunger chamber |38. The other end of the passage |36 communicates with a passage |39 which connects the passage |36 to one end of a plunger chamber |40. Within the plunger chamber |38 there is a plunger I 4| and a similar plunger |42 is disposed within the plunger chamber |40. The plungers |4| and |42 extend into engagement with the laws |3|` and |32 respectively. When fluid. under pressure is admitted to the plunger chambers, theV plungers force the jaws |3| and |32 together until the jaws engage the pin |30 on the lever |28. On the jaws being forced together, they engage the ball |34 on the valve rod 39'. If the cam follower |2161 is in any other position than that shown in Figure 14, the bringing of the jaws |3| and |32 together will move the ball |34 and consequently the valve rod 39 and valve I from the neutral position, the direction in which the valve is moved will depend upon whether the cam follower I21a is in the section I 24a or |2411 of the cam groove. The jaws will maintain the Valve rod in a position to effect movement of the hydraulic gear until the gear moves an amount suicient to bring the cam follower |21 into the position illustrated in Figure 14. In thisy position, the valve I9 will be moved to the neutral position and the hydraulicl gear will Abe stopped.

In the block IZI there are provided two passages, |43 and |44, both of which communicate with an exhaust passage |45. The passage |43 communicates with the plunger chamber |22, at the reduced portion of the plunger, and a section of the plunger compartment |30 between the ends of the plunger therein. The passage |45. communicates with a section cf the plunger compartment |40 between the ends of the plunger therein. These exhaust passages carry any leakage of oil past the plunger to the exhaust.

HAND CONTROL As heretofore stated, the control element or tilting box 6 of the hydraulic gear may be actuated by the direct application of the physical force of an operator. When it is desired to control the hydraulic gear in this manner, the control lever I is moved to the hand control position. As heretofore explained, when the control lever I 0 is in this position, the Valve 49 is so positioned that the high pressure and exhaust sides of the pump are connected together so that the pump is incapable of delivering oil under pressure for the purpose of operating the hydraulic control. The pressure on the hydraulic fluid is therefore relieved and the hydraulically operated clutch II is released so that the hand-wheels I2 are connected for operating the tilting box of the hydraulic gear. The hand-wheels I2 are mounted upon a shaft |46 extending between and j ournaled in inclined frame elements |41 and |48, as shown in Figures l, 2 and 15. On the shaft, intermediate the frame members, there is mounted a worm |40 for rotation with 'the shaft. The worm |40 engages a worm wheel |50 mounted on the end of a shaft (see Fig. 15) extending longitudinally of the frame elements |41 and |48. A clutch element IIa, is mounted on the shaft |5| which extends through the cylinder I I and a complementary clutch element IIb is mounted on the end of a shaft |52. TheV clutch is controlled by a spring and a plunger in the cylinder E I. The spring acts to close the clutch and fluid under pressure acts on the plunger to compress the spring and open the clutch. The clutch is thus a normally closing clutch so that in case of emergency and failure of the hydraulic pressure the clutch will automatically close and leave the hydraulic gear in condition for operation by the direct application of the physical force of an operator. v

When the clutch is closed, the shaft I5I connected to the shaft |52 whichs iournaled in bearing brackets |53. and |54 secured to the frame members |41 and |48. On the shaft |52 there is mounted a bevel gear |55 for rotation with the shaft. The beveledy gear I 55 meshes with a bevel gear |56 mounted upon the end of a stub shaft |51 extending into the case of the hydraulic gear. The shaft |51 (see Fig. 3) is formed integral with a cylindrical, coupling bracket |58 mounted within a projecting section |59 of the case of the hydraulic gear. The bracket |58 is provided with an innerend piece 'I58a which is journaled in a ball bearing |60, and a pair of diametrically opposite slots |58b and |530 are formed in the cylindrical bracket |58 to receive a lug |6| which is slidably mounted within the cylindrical bracket for longitudinal movement with respect thereto. The lug I6I is mounted on the end of a shaft |62 for rotational movement therewith. On a portion of the shaft |62 there is formed a square helical thread |6211v which is complementary to the internal threads on a bushing |63 into which the shaft |62 is threaded. The bushing |63 is mounted in axial alignment with the cylindrical bracket |58 and it is received within a hollow shaft |64 to which it is secured against relative rotational movement. The shaft |64 is journaled in a bearing bracket |65 and has formed on the end thereof a gear |66. The gear |56 meshes with a pinion |61 secured on the shaft of the B end of the hydraulic gear. The shaft |62 extends through the bushing |63 and is coupled to an extension I5b of the piston rod I5 by a coupling |68. The coupling |68 is such that the shaft |62 may be rotated within it relative to the rod I5, but it is prevented from any material longitudinal movement with respect to the rod I5 by the coupling. The part of the coupling |68 secured to the piston rod I5 is splined upon a projection |69 on the case of the hydraulic gear so that it is free for movement longitudinally with respect to the axis of the shafts |62 and |517 but restrained against relative rotational movement with respect to the casing of the hydraulic gear. It will thus be seen that longitudinal movement of the shaft I 62 effects longitudinal movement of the piston rod I5 and, consequently, the tilting box 6 of the hydraulic gear.

From the motion transmission train described immediately above, it will be apparent that the cylindrical bracket |58 may be rotated by rotating the hand-wheels I2. Rotational movement of the hand-wheels I2 is translated into rotational movement of the shaft |5| by the worm and worm wheel |49 and |50 and rotational movement of the shaft I5| effects rotational movement of the cylindrical bracket, when the clutch I I is closed. When the cylindrical bracket I58 is rotated, the shaft |62 is also rotated. The rotation of the shaft |62 is relative to the bushing |63 since the bushing is rotated or held sta. tionary in accordance with the shaft of the B end of the hydraulic gear. Relative rotational movement between the shaft |62 and '|53 will effect longitudinal movement of the shaft |62 and consequently movement of the tilting box 6 of the hydraulic gear. The direction of movef ment of the tilting box 6 will depeend upon the direction in which the hand-Wheels I2 are moved. When the tilting box of the hydraulic gear is moved, the B end of the hydraulic gear starts rotating, and through the pinion |61 and the gear |66, the bushing |53 is rotated in the same direction as the rotation of the shaft |62 which initiated, the operation of the hydraulic gear. This relative rotation of thebushing |63 will cause 17 a reverse longitudinal movement of the shaft |62. The hydraulic gear is, therefore, operated in accordance with the difference in movement between the movement of the hand-wheels |2 and the movement of the driven object as represented by the shaft of the B end of the hydraulic gear.

LIMIT STOPS For the purpose of preventing the driven object from moving beyond certain limited positions, there are provided limit stops which operate to prevent the hydraulic gear from driving the driven object beyond the desirable limits in either direction of its movement. The limit stops act, irrespective of whether the hand or hydraulic control is functioning, to bring the tilting box to its neutral position when the driven object approaches a limiting position. The limit stops are mounted between the frame members |41 and |48 land are operated by the shaft |52, as disclosed in Figure 15.

This shaft has a threaded section |52a. At each end of this threaded section there is secured to the shaft a block, |1| and |12. The block |1| has a lug |1|a extending in one direction and the block |12 has a lug |12a extending in the opposite direction, as clearly shown in Figures 15 and 16. Threaded on the threaded portion |52a of the shaft, there is a V-shaped bracket |13 which includes a pair of arms |13a and |13b. Through the arm |13a there is an opening in the plane of the bracket which receives a rod |14 secured in the arm by a transverse pin |15 extending through the rod |14 and into openings in the arm |13a. The pin receiving openings in the arm |13a are materially larger than the pin |15 so that the rod |14 may move a limited amount relative to the arm |13a. A stiff spring |16 acts upon a head |14a formed on the rod |14 and upon the arm |13a. The head |14a of the rod |14 is adjacent an elongated block 11 secured to a plate |18 extending between the frame members |41 and |48. The block |11 has a pair of inclined faces one of which is opposite the head |14a of the rod |14 and the other of which is opposite the head |14'a of a similar rod mounted in the arm |13b in the same manner as the rod |14 is mounted in the arm |13a. Midway between the arms of the bracket, there is mounted in the bracket a block |19 which extends through the bracket and projects from either side thereof. As the shaft |52 is rotated, the bracket |13 moves longitudinally of the shaft, it being prevented from rotating with the shaft by the engagement of the head |14a or |14a with'the block |11. As the bracket |13 approaches the block |1| the lug |1|a on the block |1| engages the lug |19 on the bracket and further rotation of the shaft |52 in the direction in which it was rotating when this engagement occurred, is prevented. Likewise `when the shaft |52 is rotating in the opposite direction, the lug |12a.on the block |12 engages the projecting endof the lug |19 on the bracket |13 when thebracket approaches close to the lug |12. Thus," further rotation of the shaft in this direction is prevented. It will thus be apparent that the shaft |52 can only be rotated in either direction a limited amount.

As previously explained, 'the shaft |52 is connected to the cylindrical bracket |58 by the bevel gears |55 and |56. Consequently the bracket |58 (Figure 3) cannonly be rotated in either direction a lmiteduamount. If the tilting box is being operated hydraulically through any one of the several hydraulic controls, the shaft |62 will i8 be hydraulically restrained against longitudinal movement and the pinion |61 on the shaftof the B end of the hydraulic gear will rotate the gear |66. During the hydraulic operation ofthe tilting box, the clutch is open so that the shaft |52 is free to rotate; it is not restrained against rotation by the engagement of the worm and worm wheels |49 and |50 as is the case when the clutch is engaged. The shaft |62, the cylindrical bracket |58 and consequently the shaft |52 are, therefore, rotated in accordance with the rotation of the shaft of the B end of the hydraulic gear. This rotation of the shaft |52 through the train of gears just described will continue until the block |1i or the block |12 engages the lug on the bracket` |13 when further rotation of the shaft |52is prevented. When this occurs, the bushing |63 continues to rotate and rotates relative to the shaft |62. This relative rotation causes longitudinal movement of the shaft |62 and forcibly moves the tilting box to the neutral position against the hydraulic pressures acting on the piston I3.

In order to prevent excess pressures being created in the piston chamber |4 when the tilting box of the hydraulic gear is thus moved to the neutral position by the action of the limit stops, there is provided a relief valve (see Fig. 4). The relief valve |88 is connected to the passage 29 and to the exhaust line 24. When the limit stops move the tilting box to the neutral position the pressure created by the movement of the piston I3 against the hydraulic medium within the cylinder is relieved through this relief valve.

When the tilting box of the hydraulic gear is being operated thro-ugh the hand-wheels I2, the clutch is engaged and the shaft |52 is rotated directly by the shaft |5|. When the hand-wheels are rotated a certain definite amount, the block |1| or the block |12 depending upon the direction of rotation of the hand-wheels, will engage the bracket |13 and prevent further rotation of the shafts |52 and |62. The hydraulic gear will then effect longitudinal movement of the shaft |62 by virtue of the bushing |63 being rotated relative to the shaft |62 by the B end of the hydraulic gear and bring -the tilting box 6 to its neutral position. The ratio of the gears involved in this train of gears is 'such that the driven object has a definite limited movement beyond which it cannot go in either direction. As previously pointed out there is no oil pressure when the hand control is in operation and consequently the relief valve has no function under hand control when the limit stops are reached.

It will be apparent that various changes may be made by those skilled in the art in the details of the embodiment illustrated in the drawings and specifically described above within the scope and principle of the invention as expressed in the vappended claims.

We claim:

1. In a mechanism for driving an object in accordance with the movements of another object, the combination comprising a movable object, a driven object, variable-speed, power driven operating means for the driven object, and control means for the power-driven operating means including a movable control member, means differentially connected to the movable and driven objects and yieldably"connected to the movable control member for actuating the movable co-ntrol member in accordance with the difference in movement between the movable and driven objects, and additional means for actuating the 19 movable control member l.to bring the driven object to a fixed, predetermined position, and means for directly connecting said additional means to said movable member to actuate the same.

2. In a mechanism' for driving an object in accordance with the movement of another object, the Vcombination comprising a movable object, a driven object, variable-speed, power-'driven operating means for the driven object and control means for said power-driven operating means including a movable control element and means for moving said movable control element in accordance with the difference Vin movement between said movable and driven objects in a one to one ratio, another movable control element, means for moving said second mentioned control element inV accordance with the difference in movement between said movable and driven objects in a ratio greater than one to one, and additional means for moving said second mentioned control element operable in accordance with the positional relation of the driven object to a iixed, predetermined position..

3. In a mechanism for driving an object in aocordance with the movement of another object, the combination comprising a movable object, a driven object, variable-speed, power-driven operating means for the driven object and control means for said power-driven operating means including a movable control element and means for moving said movable control element in accordance with the diierence in movement between said movable and driven objects in a one to one ratio, another movable control element, means for moving said second mentioned control element in accordance with the difference in movement between said movable and driven objects in a ratio greater than one to one, means operative in accordance with the positional relation of the driven object to a fixed, predetermined positiony for moving said second mentioned control element, and manually operable means for moving said Second mentioned control element.`

4. In a mechanism for driving an object in accordance with the movement of another object, the combination comprising a movable object, a driven object, variable-speed, power-driven operating means for the driven object and control means for said power-driven operating means including a movable control element and means for moving said movable control element in accordance with the difierencein movement between saidmovable and driven objects in a one toone ratio, another movable control element, means for moving said second mentioned control element in accordance with the dierence in movement between said movable and driven objects in a ratio greater than one to one, means for moving said second mentioned control element in accordance with the relation of the driven object to a fixed, predetermined position, manually operable means for moving said second mentioned control element, and means for selectively connecting said control element moving means for'operating said second mentioned control element.

5. In a mechanism for driving an object in acv cordance with the movement of another object, the Vcombination comprising a movable object, a driven object,.variablespeed, power-driven operating means for the driven object and control means for said power-,driven operating means including a movable control elementV and meansy for moving said movable control element in ace cordance with Vthe.diference,in movement be= tween said movableand drivenobjects in a `one to V,one ratio, ,anotherV movable rcontrol '.element, means for movingsaid second mentioned control element in accordance withY the difference in movement betweenv said movable and Vdrivenobjects in a ratio greater than one to one, means for moving said second mentioned control element in accordance with the relation of the driven object to a xed,.predetermined position, manually operable means for moving said second mentioned control element,4 means for renderingthe rst mentioned control element ineiective and means for selectively vconnecting said control element moving means for operating `said second mentioned controlV element.Y

6. In a mechanismior drivinganobjectin accordance with the movement of another object, the combination of a driven object, a movable object; a power unit having a rotatable element operatively connected to the driven object, a member for controlling rotation of .the element, manually operablemeansfor actuatingv the control member including a power actuated clutch, power actuated means for actuating the control member inv accordance with relative movement between .the driven and movable objects, and a connecton between .the power Yactuated means .and the power actuated clutch to actuate the clutch to disconnect the manuallyoperable means from the control element 'when the power actuated means is eiective for actuating the, control element.

7. In a mechanism for driving `an object in accordance with the movement of another object, the'combination comprising ra movable object, a drivenV object, a substantially constant speed prime mover for-driving the driven object, a variable speed transmission connecting the prime mover and the driven object, control means for said transmission including .a movable control element and Vmeans differentially connected to the movable and driven objects land yieldably connectedV to the'movable control element for moving Ksaid control element in accordance with the diieren'ce in movement between said movable and driven objects; and additional means for moving said control element accordingY to the Ydepartureof'said driven 4object from a reference position.

EDWARD J POITRAS.V JAMES'D; TEAR..

REFERENCES CITED The following references areof record in the.

iil'e oithis patent:

UNITED STATES yPATENTS 5.

Number Name Dater 1,292,029 Paine Jan. 21, 1919 1,296,303 Manly Mar. 4, 1919' 1,375,269 Akemann Apr. 19, 1921 1,387,678 Anderson; Aug. 16,1921 1,559,566 Farrell et al. Nov; 3,1925 1,612,118 Hewlett Dec.l 28, 1.926 1,747,349 f Crain Feb. 18, 1930 1,986,640 Lamond .Jan.. 1, 1935 2,019,264 l Koons" Oct.y 29, 19351 2,023,168 Erling Dec.3, 1935v FOREIGN PATENTS Number Country Date 21,436 GreatBritain 1912 428,533` Great Britain May 10, 1935 

